Street traffic signalling system

ABSTRACT

A street traffic signalling system in which the signal light units for each traffic flow of an intersection are independently regulated under the control of a central programmer with the signal unit for each traffic flow being controlled over a respective individual channel, by means of an actuating switch cooperable with and adapted to trigger respective time switches in the form of impulse counters, in combination with a timing generator which is common to the impulse counters of an intersection, which timing generator is periodically synchronized from the central station through synchronizing impulses at selected time intervals, for example, once per signalling cycle, and in which the impulses of the timing generator are sufficiently phase-shifted at the initiation of an order signal from the main station to prevent improper operation of the system and false indications in a test device.

United States Patent Obermaier et al.

[111 3,872,422 1451 Mar. 18, 1975 STREET TRAFFIC SIGNALLING SYSTEMPrimary Examiner-William C. Cooper Assistant ExaminerRandall P. Myers[75 Inventors: Anton Obermaier' Peter Drebmger 1 both of Munich; johannHoisl, ginorney A celm, 0r Farm-H1, Gross, Simpson, Van Ottobrunn, an ofGermany anten, tea man, C iara & Simpson [73] Assignee: SiemensAktiengesellschaft, Berlin & ABSTRACT Munich, Germany As t r ee t traffic signalling system in which the signal [22] Filed: June 13, 1973light units for each traffic flow of an intersection are independentlyregulated under the control of a central PP N05 9 5 programmer with thesignal unit for each traffic flow being controlled o ver arespectiveindividual channel. [30] Foreign Application Priority Data by means ofan actuating switch cooperable with and 9 2229284 adapted to triggerrespective time switches m the form June 1 72 Germany r V of impulsecounters, in combination with a timing gen- [52] U.S. Cl 340/41 R ratorwhich is common to the impulse counters of an intersection generatorFleld of Search R, 35, ynchronized from the entral tation through syn.chronizing impulses at selected time intervals, for exl l ReferencesCited ample, once per signalling cycle, and in which the im- UNITEDSTATES PATENTS pulses of the timing generator are sufficiently phase-1,625,990 4/1927 Garrett 340/40 Shifted t the initiation of an Ordersignal from the 1,756,490 4/l93O Mackall v 340/40 mam Station to preventImproper operanon of the y 3,302,170 1/1967 Jensen et al. 340/41 R temand false indications in a test device. 3,675,196 7/1972 Molloy et al340/35 3 Claims, 9 Drawing Figures E 3P Fl x l 47c SC I 851 l I E I I -r1 SE3 l SC 3 I I sch Sci. I nf. Z2 L Dr l 1 $113 sglB Ot c! e sc13 i q,1

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PATENTEDHAR I 8 I975 SHEETS [15g FFFT | I tlllllllll [Ill] scUBACKGROUND OF THE INVENTION The invention is directed to a streettraffic signalling system in which the signal light units for eachtraffic flow at an intersection are to be independently regulated by acentral programmer with the signal unit for each traffic flow beingcontrolled from an individual control channel by means of an actuatingswitch cooperable with time switches which can be triggered thereby andare in the form of impulse counters.

The use of computers for the central control of the signal light unitsof a street traffic signalling system is becoming more and moreextensive. However, their application is of primary use only when theyare able to transmit all necessary orders for the control of theintersection from such central or main station whereby no programmingoperations are effected at the intersection itself. In order to achievethis result with a minimum of control channels, the signal light unitsfor each traffic flow, which must be independently controlled, arecontrolled over a single individual control channel in cooperation withtime switches which can be triggered by the actuating switch and whichare in the form of impulse counters. This thereby permits the individual control of each signalling state at the intersection involved fromthe main station. However, no dangeroustraffic conditions shall occur asa result of the release of opposing traffic flows as they may resultfrom the geometry of the intersection, and thus safety devices must beprovided at each intersection. As safety devices now employed operatewith electronic switching circuits and thus would also determine shortfaulty switchings of the signal lamps, overlapping signal changes mustbe safely avoided.

BRIEF SUMMARY OF THE INVENTION The invention is directed to the problemof efficiently combining these two requirements whereby the entiretraffic operations of an intersection may be centrally programmed anddetermined with as few as possible transmission means between theintersection and the computer programmer in the main station, at thesame time avoiding any possible dangerous traffic conditions which mightarise by the utilization of fast reacting test devices.

According to the invention, these results are achieved in a streettraffic signalling system employing a central programmer at the mainstation in which the signal light units for each traffic flow at theintersection involved, which must be independently adjusted, arerespectively controlled over one individual control channel incooperation with an actuating switch and timing switches triggerablethereby, and which may be in the form of impulse counters, which suchimpulse counters also being under the control of a local timinggenerator common to all of those at such intersection, and which timinggenerator can be synchronized from the main station by means of asynchronizing impulse at predetermined selected time intervals as forexample once per programmed signalling cycle, with the impulses of thetiming generator being sufficiently phaseshifted at the initiation of achange order signal from the main station, with such time delaypreventing the undesired operation in the test device. Advantageously,the synchronizing impulse from the main station can be transmitted tothe intersection over a special control channel", or such synchronizingimpulse can be derived at the intersection from the impulse flank of asignalchanging order from the main station.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, wherein likereference characters indicate like or corresponding parts;

FIG. 1 is a diagram illustrating a simple traffic intersection with thetraftic flows involved and associated signal units for the controlthereof;

FIG. 2 is a circuit arrangement including a central programmer in themain station and a signal light unit or assembly at an intersection;

FIG. 3 is a time chart for the signal units regulating the intersectionin accordance with FIG. 1;

FIG. 4 is a circuit diagram of a control device associated with each ofthe signal units;

FIG. 5, is a table illustrating various related states of certaincomponents of the circuit of FIG. 4;

FIG. 6 is a circuit diagram of a control device for pedestrian signalunits;

FIG. 7 is a circuit diagram of a timing generator for use in the circuitof FIG. 2;

FIG. 8 is a time chart in connection with the operation of the timinggenerator of FIG. 7; and

FIG. 9 is a circuit diagram of a test device for monitoring thesignalling operations.

1 DETAILED DESCRIPTION OF THE INVENTION regulated by eight signal unitsor indicators, each of which contains the associated signals lamps forthe desired control, the signal units Sgl through Sg4 being provided forthe control of the vehicle flow and the signal units sgll through sgl4being provided for the regulation of pedestrian traffic. It will beapparent that traffic flows 3, 4 and pedestrian flows I3, 14 must beblocked when the vehicle traffic 1 is released to avoid the dangers thatwould otherwise arise. The corresponding red or stop lamps in theassociated signal units Sg3, Sg4 and sgl3, sgl4 must thus be illuminatedwhen the stop lamp in, the signal unit Sgl is extinguished. This resultis monitored by a test device Pe as will subsequently be explained withrespect to FIGS. 2 and 9, respectively.

In order to be able to control the traffic flows at the streetintersection Kr from the main station Ze, illustrated in FIG. 2, controldevices Stl to 8:4 are provided for the respective vehicle signal unitsSgl through Sg4 and control devices szll throughstl4 are provided forthe pedestrian signal generators sgll through sgl4 (For simplicity andto avoid mere duplication, signal unit sg2, sgll and sglZ have beenomitted from the drawing).

All component elements illustrated in FIG. 2 are designated byreferencecharacters comprising two letters, while component elements inthe individual devices SI, st, Tg, Pe, etc., are designated by referencecharacters comprising one letter.

The control devices St or st can be controlled in conjunction with acommon timing generator Tg at the intersection Kr by the programmer Pgin the main station Ze, Pa control channel F1. The programmer pg isrepresented symbolically in FIG. 2 by a rotary selector Dr andinformation contact Inf. This is intended to .broadly depict theactuating switches Scl through usually employed with computers which canbe in the form of intermediate memories, such'as the buffer memorySp.

therefore are not simultaneously transmitted from the main station Ze tothe individual signal units Sgl through sg14, but with a slight mutualphase shifting. As will be subsequently explained in connection with thetest device Pe, this prevents the respective stop lamps involved fromimmediately lighting which otherwise might result in illumination of thecontrol lamp S1 as a warning, with the entire signalling system possiblybeing simultaneously cut off at the intersection Kr by opening of theswitch sch.

For a further explanation of this type of over-lapping signal change andthe possibilities of avoidance thereof reference is made to FIG. 3.Section 0.) of this figure discloses that the switches 801 through Sc4or Scll through S014 only switches Scl, Sc3, S04, Sc13, and S014 beingillustrated in the figure.) are actuated sequentially within a timeperiod between and 1 second, and thus the actuation of the controldevices Stl through st14 are actuated with a corresponding phase shift.Consequently, if the second impulse from the timing generator Tg wereemitted when all orderdesignating signals had been transmitted for thedesired signal change in this period between 0 and 1 second,

With each change in signalling state, the orders possibly all controldevices Stl throughsll4 would be simultaneously switched and thus alsothe signal units Sgl through sg14 (comparesection b of FIG. 3). Theindividual signal conditions red, red/yellow and green for the signalunits Sgl through sg14 are presented in section 0 of FIG. 3 in which therepresentative time period is correspondingly changed to provide abetter illustration. The phase shifting of the timing impulses withrespect to the order-designating signals is achieved by timing meansinthe timing generator Tg which allows a minimum time of 500 millisecondsto occur between the sychronizing impulse from the switch 500 and thetiming impulses.

FIG. 3 also illustrates how an order-designating signal, for example,that for the signal generator Sgl can also be employed as asynchronizing impulse. Thus, in Section (a.) the leading flank of theorder-designating signal, as indicated in solid sectioning and thearrow, may be so'employed.

FIG. 4 illustrates the construction of the control devices St for theindividual vehicle signal units Sg. Assuming that no voltage is appliedat the input q thereof, the flip-flop Kl will be in rest position overits inverted input, as indicated by the clot. The flip-flop K2 likewisewill be in rest position. A voltage thus will appear at their outputsal, and the red lamp in the signal unit Sg will be illuminated.

If a voltage is now applied to the input q from the main station Ze,upon the appearance of a corresponding impulse from the timing generatorTg at the input u, K1 will be flipped into operational condition. Avoltage thus will appear at the outputs of Nand gates G1 and G2 wherebythe yellow lamp will be illuminated over the Nand gates G3, G4.Simultaneously, however, the counter Z1, which previously was maintainedin zero position over its reset input R,,, will be actuated and after agiven time period, for example, after three seconds, the counter Z1 willemit an impulse which will be conducted to Nand gates G5, G6, which incooperation with an impulse from the timing generator Tg, will flip theflip-flop K2 into operational condition. A voltage will therefore appearat the output K2 thereof which will be conducted over Nand gates G9,G10, and additional power switches, not illustrated, to extinguish thered and yellow lamps in the signal unit Sg and illuminate the greenlamp. At the same time, the counter Hui". bsle s 9v, nPPt If the voltageat the input q ceases, as a result of it being cut off at the mainstation Ze upon receipt of the second timing impulse from the input u,flip-flop Kl will return to its rest condition. This will result in acutting off of the actuation of the green lamp over the Nand gates G9,G10, while Nand gates GI through G4 will result in illumination on theyellow lamp without actuation of any further means. At the same time,the reset input R of the counter 21 is released and after a given timeperiod, for example, 4 seconds, the flip-flop K2 will be returned to itsrest position over Nand gates G7, G8, cooperably with the secondimpulseat the input u. Now, only the red lamp in the signal unit Sg willbe illuminated and the counter Z1 will be returned into its zerocondition. The control device St is also provided with two Nand gatesG11, G12 whereby a voltage will always appear at the output v when onlythe red lamp is illuminated in the signal unit Sg.

FIG. 5 illustrates the conditions at various components of the controlcircuit as well as illuminating conditions of the red, yellow and greenlamps in the signal salt 8- V 1 FIG. 6 illustrates a simple controlswitch st for the pedestrian signal sg. If no voltage is present at theinput q, the flip-flop K3 will be in its rest position and the red lampwill be illuminated in the signal unit sg. However, if a voltage isapplied to the input q from the main station Ze, upon receipt of thenext following impulse from the timing generator Tg, the flip-flop K3willbe flipped into its operational position, and the green lamp in thesignal unit sg will be illuminated. Likewise, a voltage will appear atthe output v only when the red lamp is illuminated. I

FIG. 7 illustrates a circuit for the common timing generator Tg for theintersection Kr. Initially, no voltage is at the input w, so thatflip-flops K4 and K5 are in operational position as the input e2 of theflip-flop K4 is inverted, as indicated by the dot. Alternating voltageof 50 Hz frequency is present at the input .r and timing generator Tthus will apply a frequency of 100 Hz of the flip-flops K4, K5 and thecounters Z3, 24. The latter are adapted to function as frequencydividers and respectively emit onc impulse per second over Bland gatesG15, G16 to the output y.

Upon the arrival ofa synchronizing impulse over the switch Sc 0, scofrom the main station Ze, at the input w of the timing generator Tg,flip-flops, K4, K5 will be returned into their rest positions, one afterthe other, by the two following impulses of the timing generator T. Atthe intermediate phase, when the flip-flop K4 is in rest position andflip-flop K5 in operational position, the counters Z3, Z4 will receive areset impulse over Nand gates G13, G14 applied at the reset inputs R,,,R which synchronizes the counters Z3, Z4 and brings them into thecounting position 500. The impulse following the synchronized impulse atoutput y will therefore be emitted after 500 milliseconds. This, as willbe noted from FIG. 3, will shift the second impulse from the timinggenerator Tg with respect to the synchronizing impulse from the mainstation Ze by 500 milliseconds. Thus, any danger of an over-lappingsignal-image change will be eliminated.

In FIG. 8, the phase relationship existing between the th and 21stseconds, illustrated on the time axis t are shown for the synchronizingimpulse from the switch sea, the impulses from the timing generator T,the switching functions of the flip-flops K4, K5, Nand gate G14,counters Z3, Z4, as well as the time delay tv=500 milliseconds betweenthe synchronizing impulse and the timing impulse of the timing generatorTg.

FIG. 9 illustrates the construction of the test device Pe in which theindividual outputs vl-through v14 of the control devices St or st,illustrated in FIG. 2, have been interlinked in a predetermined logicover Nand gates G17, G18, G19 and the Or gates 01, 02.

Thus, no voltage will appear at the output of the common Nand gate G19as long as the red lamps are illuminated in the respective signal unitunder which circumstances no dangerous traffic conditions can occur. Ifone of such red lamps fails the warning lamp S1 will be illuminated inthe main station Ze, over the common Nand gate G19, and simultaneouslythe entire signalling system at the intersection Kr will cut off bymeans of the switch Sch, sch.

Although various minor modifications might be suggested to those versedin the art, it should be understood that I wish to embody within thescope of the patent warranted hereon all such modifications asreasonably and properly come within the scope of my contribution to theart.

We claim as our invention:

1. In a street traffic signalling system in which the signal light unitsfor the traffic flow in each direction at an intersection areindependently regulated under the control of a central programmer at amain station with the signal unit for each such traffic flow beingcontrolled over a respective individual channel, the combination of anactuating switch, controlled by said programmer, for each channel atsuch main station, operative to transmit order signals to the associatedunit, time switches, for the respective units, in the form of impulsecounters adapted to be triggered in response to an order signalresulting from actuation of the cooperable actuating switch, a timinggenerator connected in common to the respective impulse counters of anintersection for supplying impulses thereto, said timing generator beingconnected to receive synchronizing impulses, from the main station, atselected time intervals, whereby such generator is periodicallysynchronized, for example, once per signalling cycle, said timinggenerator including means for effecting a phase-shifting of the timingimpulses upon the initiation of an order signal from the main station,for preventing improper operation of the system and false indications ina test device.

2. A street traffic signalling system according to claim 1, whereinthere is provided an additional individual channel over which saidsynchronizing impulses are transmitted to said timing generator. I

3. A street traffic signalling system according to claim 1, wherein saidtiming generator is connected to be responsive to the leading edge of anorder signal as the synchronizing impulse.

1. In a street traffic signalling system in which the signal light unitsfor the traffic flow in each direction at an intersection areindependently regulated under the control of a central programmer at amain station with the signal unit for each such traffic flow beingcontrolled over a respective individual channel, the combination of anactuating switch, controlled by said programmer, for each channel atsuch main station, operative to transmit order signals to the associatedunit, time switches, for the respective units, in the form of impulsecounters adapted to be triggered in response to an order signalresulting from actuation of the cooperable actuating switch, a timinggenerator connected in common to the respective impulse counters of anintersection for supplying impulses thereto, said timing generator beingconnected to receive synchronizing impulses, from the main station, atselected time intervals, whereby such generator is periodicallysynchronized, for example, once per signalling cycle, said timinggenerator including means for effecting a phase-shifting of the timingimpulses upon the initiation of an order signal from the main station,for preventing improper operation of the system and false indications ina test device.
 2. A street traffic signalling system according to claim1, wherein there is provided an additional individual channel over whichsaid synchronizing impulses are transmitted to said timing generator. 3.A street traffic signalling system according to claim 1, wherein saidtiming generator is connected to be responsive to the leading edge of anorder signal as the synchronizing impulse.